From EP 0 466 863 B1 there is known a device for connecting a driveline in a motor vehicle with a transfer case for a plurality of drivelines. One of the drivelines is permanently connected to a drive unit and a further driveline can optionally be connected to the drive unit. For connecting the driveline, there is provided an electronically actuated friction coupling which can be arranged in a transfer case or in a differential drive.
DE 10 2008 037 885.2-21 proposes a drive assembly with a hang-on coupling and a differential unit for a multi-axle driven motor vehicle. The hang-on coupling is provided in the form of a friction plate coupling which is arranged coaxially relative to the axis of rotation of the differential carrier of the differential unit.
From DE 39 13 487 A1 there is known a four-wheel drive tractor whose front axle differential and rear axle differential are driven permanently during off-road applications. In order to prevent any distortions between the front axle and the rear axle there is provided a coupling between the ring gear of the rear axle differential and the differential carrier. The coupling is ventilated via an actuating cylinder and can thus be controlled under conditions of slip. In the unpressurized condition of the actuating cylinder, the coupling is loaded by a plate spring so that torque is transmitted from the front axle in a rigid through-drive to the rear axle.
From DE 42 02 026 A1 there is known a drive assembly for controlling and distributing the driving force for a motor vehicle which comprises two driven axles. The drive assembly comprises a rear axle differential which is controlled via a first valve, a front axle differential lock which is controlled via a second valve, and an intermediate differential lock which is controlled via a third valve. Said valves are electro-hydraulic valves which receive their hydraulic pressure from a pump.